Telephone-exchange system



Aug. 18, 1925.

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TELEPHONE EXCHANGE SYSTEM Filed July 25, 1921 13 Sheets-Sheet 13 /f/z ve//z far- /4/bm f L ande/A .l?. n Bbw/@M ,4 ff y Patented Aug. 18, 1925.

UNITED STATES PATENT OFFICE.

ALBEN E. LUNDELL, 0F NEW YORK, N. .Y., ASSIGNOR '.lO WESTERN ELECTRIC COH- i PANY, INCORPORATED, 0F NEW YORK, N'. Y., .A

CORPORATION or NEW Yoizx.

TELEPHONE-EXCHAN GE SYSTEM.

Application lled July 25, 1921. Serial No. 487,520.

To all 'uf/10m it muy concer-n: Y

Be it known that I, ALBEN E. LUNDELL, a citizen ol' the United States, residing at New York, in the county of Bronx, State of New York, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to automatic telephone exchange systems, and more particularly to exchange systems of large capacity.

It is the object of this invention to provide an improved full automatic exchangel system capable of giving rapid and efficient service.

It is a further object of the invention to provide in'iprovement suitable for use in connection with any type vof automatic system, whether full-automaticor semi-automatic.

It is also an object of this invention to provide an improved registering and controlling equipment.

An additional object of the invention is the provision of an improved line switch circuit.-

A feature of the invention resides in the use of a translator switch, or secondary registering device, and the means of controlling the same. A further feature resides in the mcthodof shitting control suc-.

cessively to the various registering devices.

Added Afeatures may be found in the method of associating a register and controlling equipment with a switching link; in the method employed for settingA up the class of service registration; and in various I other novel circuit arrangements which will be more clearly apparentfrom the following description and the appended claims.

A still further' feature of the invention relates to a method for causing the restoration of the individual line switch in a. minimum of time.

Referring to the drawings, Figure 1 shows a circuit of a line switch individual to a. calling subscriber; Figure 2 shows a circuit of a district selector switch, and a controlling sequence switch therefor; Figure 3 shows a class and controlling sequence switch and various auxiliary' relays; Figure 4 shows a register control switch and one of the register switches; Figure 5 shows a second register switch and indicates diagrammatically, portions of a translator switch which is positioned under the joint control of the lirst two registers. The thousands register is also shown in this figure. Figure 6 shows the sender circuit inclmlmg counting relays and a controlling sequence switch, together with various relays; Figure 7 shows a sequence swatch used for sending impulses 1n case a call 1s to be extended to a relay call indicator operator`s position. Hthin the dotted square in the lower le it-hand portion of this figure are shown contacts controlled by the class sequence switch of Figure 3. Figure 8 shows the remaining register switches; Figure 9 shows the circuits of an otlce selector switch; Figure 10 shows the arrangement o't' lletters and numerals on a dial suitable .for use with a system ofA the type disclosed in this application; Figure 11 shows more completely the circuits ofthe translator various sheets should be placed in order to` properly coordinate the various circuits.

It is thought that the invention will best be understood from a detailed description of the operation of the system, reference being had to the accompanying drawings.

'hen the subscriber at substation 1 removes his receiver from the switchhook, a circuit is completed from grounded battery, vinding of line relay v2, inner lower armature and back contact of cut-off relay 3 through the loop of the calling substation line, upper armature and back contact of relay 3 to ground. Line relay 2 is energized in this circuit and attracts its armatures. Since the test brush 5 is in engagement with its normal contact and since its normal contact is connected to ground, the energization of linerelay 2 completes a circu1t from grounded battery, winding, armature and back contact of stepping magnet 4, lower armature and back contact of cut-oit relay 3, right-hand armature and front contact of the line relay 2, conductor 15, test brush t3, normal terminal 19 to ground. Magnet 4 is energized, and upon energization interrupts its own circuit to release its armature and advance the line switch into its first .olfnormal position. As soon as the line switch makes its first step, oit-normal contact closes and olf-normal spring 14 releases its upper contact and engages its lower contact. Off-normal contact 14 removes the control of the cut-olil relay from any line which may be calling and supplies battery to test terminal 1G to render the calling line busy to other calling subscribers. The test teru'iinals of trunks extending to busy district circuits will be characterized by the presence of ground potential on such test tcrminalsas will be evident from the following description. As long as test brush 5 engages contacts oiE busy trunks ground will be supplied to conductor 15 and stepping magnet .4 will continue to interrupt its own circuit to cause the advance of the line switch. As soon as test brush 5 engages a terminal on which there is no ground potential the circuit for magnet 4 is opened, and the switch is brought to rest with its brushes on the terminal set of an idle trunk leading to an available district selector.

It should be noted that during the opera tion of this switch a circuit is in existence for cut-off relay 3 extending from ground, upper and lower windings of cut-of relay 3, left-hand winding of line relay 2, left-hand armature and front contact of relay 2, righthand armature and front contact of relay 2, lowermost armature and back contact of cut-off relay 3 and thence to grounded battery through the winding of magnet 4, Cutoft relay 3 cannot, however, be energized `in this circuit since its winding is short-circuited by the direct ground supplied to conductor 15 by way of test terminals 9. As soon as the brush set comes to rest on the selected terminal set, a circuit is completed from grounded battery, resistance 199 (Fig. 2), contacts of sequence switch spring 198, armature and back contact of relay 102, conductor 106, terminal 9, test brush 5, conductor` 15, left-hand winding, armature and front contact of line relay 2, through the windings of cut-off relay 3 to ground. The presence of battery potential at terminal 9 short-circuits magnets 4 and allows cut-off relay 3 to operate. The operation of cut-ott` relay 3 causes the deenergization of line relay 2.

A circuit is then completed from grounded battery (Fig. 2), right-hand winding of relay 102, armature and back contact of relay 139, lower right-hand contact of sequence switch spring 103, sleeve conductor 104, tei'- minal 11, brush 7, winding of message register magnet 17, lower mic dle armature and front contact of relay 3, lower holding winding of relay 3, to ground. Relay 102 is energized and at its inner left-hand armature and front contact supplies ground by way of conductor 105, to test conductor 106 and its associatedtest contacts, to render this trunk non-selectable to other hunting line switches. The energization of relay 102 also completes a circuit from grounded battery, right-hand winding of relay 107, upper left-hand contact of sequence switch spring 108, lower contacts of sequence switch spring 109, right-hand armature and front contact of relay 102 to ground. Relay 107 is energized in this circuit. Assuming that the sender on the terminals of which the brushes of the sender selector are resting i's busy and that this busy condition is indicated by the presence of ground on the test terminal of such sender, a locking circuit for relay 107 is completed from grounded battery, lefthand winding and left-hand armature and front contact of relay 107, conductors 110 and 111, upper left-hand contact of sequence switch spring 112, lower left-hand contact of sequence switch spring 113, conductor 114, test brush and its associated test terminal, to ground. Relay 107 also completes a circuit from grounded battery, power magnet of sequence switch 100, lower right-hand contact of sequence switch spring 116, inner right-hand armature and front contact of relay 107, lower contact of sequence switch spring 117, to ground, for moving this sequence switch out of position 1 and into position 2 under the control of its master spring contact 101.

In position 2 of sequence switch 100 a circuit is completed for causing the selection of an idle sender. The circuit for the sender selector stepping magnet 118 is completed from grounded battery, armature and back contact of magnet 118, winding of magnet 118, conductor 119, lower contact of sequence switch spring 120, inner righthand armature and front contact of relay 107, and the lower Contact of sequence switch spring 117 to ground. Stepping magnet 118 interrupts its own circuit and causes the advance of the sender selector brushes until an idle sender is found. When an idle sender is found the absence of ground on the test terminal of such sender breaks the locking circuit of relay 107 and this relay deenergizes, at the same time opening the circuit of stepping magnet 118 and bringing the sender selector to rest. Relay 107 upon deenergization also completes a circuit from grounded battery, power magnet of sequence switch 100, upper righthand contact of sequence switch spring 116, inner right-hand armature and back contact of relay 107 lower contact of sequence switch spring 117 to ground, for moving this sequence switch out of position 2 and into position' 3.

During the hunting movement of the sender selector a circuit is in existence from grounded battery, armature and back contact of stepping magnet 118, winding of magnet 118, winding of relay 121, lower contacts of sequence switch spring 122, inner left-hand armature and front contact of relay 102, to ground. The presence of direct ground on conductor 119 lshunts relay 121 at this time to prevent its operation. However, as soon as relay 107 is deenergized this shunt is removed and relay 121 is energized to connect the controlling leads to the selected sender. Relay 121 atits inner lefthand armature supplies ground to the terminal associated with test brush 115 to render the sender non-selectable by other sender selectors.

As soon as the sender has been seized and relay 121 has operated, a circuit is completed from grounded battery, through the winding of relay 202 (Fig.4 3), upper leftliand and lower right-hand contacts ot' sequence switch spring 203, conductors' 204, and 205, test brush 115 and its associated contact, conductor 114, inner left-hand armature and front contact of relay'121 to ground. Relay 202 is energized and completes a-circuit from ground, outer righthand armature and back contact of relay 206, outer left-hand armature and front contact of relay 202, outer left-hand armature and back contact of relay 207, conductors 208, and 209, outer right-hand armature and back contact of relay 210, conductors 211 and 302, upper right-hand contact ot' impulser sequence switch spring 402, winding of power magnet 400 ot' the impulser sequence switch, to grounded battery. Power magnet 400 is energized in this circuit and advances the impulser sequence `switch out of position 1 and into position 13 under the control of the master spring 401. The purpose of the movement of the impulser sequence switch at this time is to provide the same time interval necessary before dialing tone is supplied, in case the subscriber is connected to the district by means of a line switch instead ofby a line finder. When sequence switch 40() reaches, position 5, a

circuit is completed from ground d battery,

winding of relay 207, conductors 212 and 303, upper left-hand contact of sequence switch spring 403 to ground. It is, of course, obvious that the time which expires before relay 207 is energized, may be controlled by varying the cutting-ot sequence switch spring 403 so that agreater or less time will be consumed before relay 207 is energized. Relay 207 upon energization, locks up through its outer right-hand armature and front Contact to grounded conductor 205, and at the 'same time connects through the calling subscribei"s line to the sender, incidentally supplying him with a dial tone to in'l'orm him thathe is free to dial. Relay 20T upon energization also completes a circuit trom grounded battery, winding ot' sequence switch magnet 200, upper right-hand contact ot' Sequence switch spring 219, outer left-hand armature and front contact of relay 207, left-hand armature and front contact oi relay 202, outer right-hand armature and back contact of relay 200, to ground for moving this sequence switch out of position 1 and into position 3, under the control of its master sequence switch spring 201.

The primary circuit of the induction coil by means of which the dialing tone is supv plied to the calling subscriber extends from a suitable source of tone through the lefthand winding of induction coil 213, conductor 214, register brush 500 in its normal position, conductor 501, outer left-hand armature .and back contact of relay 502, to ground at the right-hand armature and back contact of slowto-release relay 503. The current in this circuit is induced into the receiver of the calling subscribers substation set over a circuit extending from grounded battery, winding of line relay 215, conductor (516, inner lett-hand armature and back contact of relay 600, conductor 601, inner right-hand armature and front contact of relay 207, conductor 216, sender selector brush Y123 and its associated Contact, outer lett-hand armature and front contact of relay 121, conductor 121, upper lett-hand contact of sequence switch spring 125, conductor 120, through the Contact of the. line switch to the calling subseribers station, through the tip contacts ot the line switch` conductor 127, upper left-hand contact ot' sequence switch spring 12S, conductor 120, sender scleetor brush 130, and its associated Contact, conductor 131, inner lett-hand armature aud front contact of relay 207, conductor 617, right-hand armature and back contact ot' re lay 600, conductor G02, right-hand winding ot' induction coil 213 to ground. lV hen the calling subscriber hears this dialing tone he operates his sub-station dial to send out series of impulses to the set of registers in the selected sender.

It will be assumed that the line to be selected is one which tern'iinates in aA full mechanical exchange, which may be selected dia number of more than four digits, confusion is apt to result. However. if an office name is used in connection with tour digits, he can readily remember this. It is, therefore, proposed to provide the subscriber with a dial in which each digit has an accompanying letter or letters. It then the subscriber is instructed to dial the tirst two letters of the desired exchange name and then the digits of the wanted line in the exchange, the desired size ot installation and range of connections may be accomplished without cansing any confusion to thek subscriber. Assuming that the wanted line is Grand 5678, an inspection of Fig. 10 will show that the subscriber will tirst insert his finger in the hole containing the letter G and the digit 3 to send :tour impulses. He will then operate his dial to send the letter ll or S impulses after which he will send series ot G, 7, S and 9 impulses respectively.

In order to more fully understand the operation of the above mentioned dial, it will be necessary to refer to Fig. 10 of the drawing. It will be noted that the zero of this dial is in the position usually alloted to numeral 1. This change was made as it was necessary in the operation of applacants sender to register one impulse for the digit zero. For this reason, one eXtra impulse is Set out for each succeeding numeral such as four impulses for No. 3 and ten impulses for No. 9.

In order to prevent confusion as to which switches the various brushes and contact arcs shown in Figs. t, 5 and 8 are related the brushes belonging to the progression switch or side switch have been indicated by the letters SS the arms belonging to the register which is set in response to the tirst series of impulses of the otlice code have been designated by the letter A.; the arms belonging to the register which is operated in response to the second series ot impulses ot the office code have been designated by the letter l; the brushes ot the thousands register' are identified by the letters TH; and those of the hundreds, tens, and units register have been designated by the letters H, T, and U, respectively. The three registersshown at the right in Fig. S, have not been described. These registers are provided in order to allow a calling subscriber' to dial the digits ot' a wanted station in a P, B. X. exchange. Since they are not brought into use in the ordinary operation of the system and since they are -not necessary to an understanding of the various features of the invention, their operation has not been described.

The various contact controlled hy sequence switch 4100 (Fig. 7) are used to control indicating lamps at a relay call indicator operators position. It was necessary to shew sequence switch 400 since 1t is used for measuring a time interval, but since the operation of relay call indicators is Well-known in the art, it has not been considered necessary 'to describe the complete operation of the impulse switch in case a call is extended to a relay call indicating position.

Relay 215 is energized upon the completion ot' the above traced dial tone circuit and causes in turn the energization ot slowto-release relay 217, which in turn causes the energization of relay 218. rIhe first interruption due to the operation of the calling subscribers dial, causes the deenergization of relay 215. This interruption being ol short duration, however, relay 217 holds over, thereby i'naintaining relay 218 also in energized condition. Upon the deenergization of relay 215 a circuit is completed from grounded battery, resistance 501, winding ot' relay 503, conductor 523, winding of magnet 505, which controls the advance of the Af register, conductor 506, side switch brush 507 and its normal contact, conductor 508, inner left-hand armature and front contact ot' rela-y 218, armature and back contact of relay 215, to ground. Stepping magnet 505 is energized to cause the register to advance one step. Relay 503 is energized and being slow to release, remains energized until the completion of the series of impulses. In response to the first series ot' impulses the relay 215 is deenergized 4 times and upon each deenergization causes the stepping magnet 505 to advance theregister brushes one step. Upon completion ot' the series of impulses, the A register will be in its third off-normal position.

At the termination ot the series of impulses, relay 215 maintains its armature attracted for a relatively long period of time with the result` that relay 503 is deener- `gized. Upon the deenergization ot relay 503 a circuit is completed from ground at the right-hand armature and back contact of relay 503, through the winding ot relay 51S), conductor 509, upper left-hand and lower right-hand contact oi sequence switch spring 220, conductor 221, through the station register brush 511 and its normal contact, and thence through brushes 512, 513, 514, 515, 510 and the respective normal contacts of the units, tens, hundreds, thousands and B registers respectively, thence through brush 517 ofthe A register, which, due to the fact. that this register has been positioned, is in some ott-normal position, conductor 518, armature and back contact of magnet 505, windings ot magnet 505 and relay. 503'to battery. Relay 503 and magnet 505 do not energize in series with relay 519. Relay 51S) is energized in this circuit and completes a circuit from grounded battery, winding of side switch stepping magnet 520, and armature and back contact of magnet 520, conductor 521,

left-hand armature and back contact of relay 503, side switch brush 522 and its normal contact, left-hand armature and front contact of relay 519 to ground. Magnet 520 is energized and moves the side switch out of its normal position and into position 1.

It should be observed that the side-switch, which comprises brushes 507, 522, 586 and 581, is preferably of the same mechanical construction as the register switches. The preferred form of mechanism is similar to that shown and described .in the patent to O. F. Forsberg and R. M. De Vignier, 1,472,465, issued October 30, 1923.

The calling subscriber now sends the second series of impulses in order to position the B register. The first interruption of the line circuit will cause the deenergization of line relay 215, whereupon a circ-uit is completed from grounded battery, re-

sistance 504, winding of slow release relay 503, conductors 523 and 524, winding of stepping magnet 525 which controls the B register, conductor 526, side-switch arm 507 which is in Contact with its first olinormal terminal, conductor 508, inner lefthand armature and front cont-act of relay 218, armature and back contact of relay 215 to ground. Stepping magnet 525 and relayl 503 are energized in this circuit. Relay 503 being slow to release retains its armature attracted until the completion ot the series of impulses. Upon the next closure of the line circuit, line relay 215 a-ttracts its armature and magnet 525 releases toadvance the B register one step. At the conclusion of the sending of the second series of impulses, the B register will be in position 8. At the conclusion of the series of impulses, line relay 215 remains energized for a relatively long period of time with the result that relay 503 becomes deenergized. The deenergization of relay 503 completes a circuit from grounded battery, winding of side-switch stepping magnet 520, armature and back contact of magnet 520` conductor 521, left-hand armature and back contact. of relay 503, side-switch brush 522 in its first position, conductor 527, brush 528 of the B register. which is now in an oit-normal position, to ground. Magnet 520 is energized and interrupts its own circuit to cause the advance of the sideswitch into position 2. I

In position 2 ot the side switch, the impulse circuit is diverted to stepping magnet 529 of the thousands register by way of sideswi tch brush 507 and its second contact and conductor 530. Relay" 503 and stepping magnet 529 are energized in series and 'relay 503 remains energized during the sending of the series of impulses while stepping magnet 529 causes the` advance of the thousands register into position 6.

Upon the completion of the sending of the thousands impulses, the side switch is advanced into position 3 over a circuit extending from grounded battery, winding of stepping magnet 520, armature and back contact ot' magnet 520, conductor 521, left-hand armature and back contact of relay ,503, side switch brush 522 and its second contact, thence by way of conductor 531 to the thousands register brush 532, which is now in an olf-normal position, to ground. The completion of this circuit advances the side switch into position 3. y,

The setting of the hundreds, tens and units registers is accomplished in substantially the manner described, since .stepping magnets 533, 534 and 535 are successively brought under the control ot' line relay 215 as the side switch arm 507 advances from position to position. Upon completing the setting of the registers, the side switch arms Y will be in contact with their No. 5 terminals.

As soon as the A and B registers have been positioned, at which time the side switch will be in'position 2, a circuit is completed from grounded battery, winding of relay 502, side switch arm 586 and its associated contact, conductor 537, right-hand armature and front contact of relay 218 to ground. Relay 502 is energized and completes a locking circuit for itself extending from its inner right-hand armature and front contact to conductor 538, conductoi` 273, upper left-hand contact of sequence switch spring 27 4, to ground.

The setting of the translator switch will now be described. The translator switch has two sets oli' brushes, which are herein designated generally as T? and T2. After being set into motion, the translator will hunt for aposition controlled by the joint setting of the A and B registers.

Tlie'translator switch is of such simple construction that it has not been necessary to provide a drawing of its mechanism. Two arcuate contact banks, eac-h comprising a number of contact sets and each contact set comprising a plurality of contacts, are arranged side by side and supported by a suitable frame. A brush shaft carrying two 'brush sets arranged to cooperate with the contact sets, -is mounted in operative rela tion to the contact banks in the same frame. The brush sets are 180 apart in rotation, that is. they are diametrically opposite yone another on'the shaft. and the arrangement is such that lwhen one brush set completes its travel ,over its associated contact bank` the other brush set will begin its'travel over its associated contact bank. Power' is transmitted to the shaft from a constantly x rotating shaft by means ot clutch discs magneticallv controlled in the manner commonly employed in the construction of sequence conductor 547,

switches. The power source is indicated in the present disclosure'by magnet 540. Since the brushes are driven at high speed, a stop magnet, represented in the drawings by magnet 541, has been provided in order to insure their stopping on the desired terminal set.

As soon as relay 502 is energized, a circuit is completed from grounded battery, resistance 542, right-hand armature and back contact of relay 543, conductor 544, winding of power magnet 540, conductor 545, inner left-hand armature and front Contact of relay 502 to ground. Power magnet 540 is energized and starts the translator switch into operation. In order to prevent needless confusion ot' the drawings, the complete interconnections ofthe various contact arcs of the A and B registers have not been shown in Figs. 4 and 5. In orderto obtain a more complete understanding of the circuits which determine the positioning ot' the translator. reference may be had to Fig. 11 which shows the interconnections more completely.

Referring then to Fig. 11. it will be seen that the translator. after being put in motion, will continue to revolve until test brush 546, which serves the bank designated at T2 reaches contact No. 12, at which time a circuit will be completed from grounded battery, right-hand armature and back contacts of relay 543, low resistance lett-hand winding of relay 543, conductor 547, A register brush 548 and Contact No. 3, conduct-or 549, Bl register brush 550 and its associated terminal No. 7, conductor 551, the No. 12 contact in the are served by brush 546, conductors 552 and 545 to ground at the armature and front contact of relay 502. The low resistance of the lett-hand winding of relay 543 shunts down the power magnet and brings the translator switch to rest.

I )uring the hunting operation of this switch a circuit was in existence for stop magnet 541, this circuit extending from grounded battery. winding of magnet 541, low resistance ,left-hand winding of relay 543, conductor 544, outer r1ght-hand armature and back contact of relay 543, winding of power magnet 540 to ground at the armature and front contact o f relay 502. The current flowing in this circuit is not suiicient to allow magnet 541 fto become energized, but it does se-t up enough magnetism so as to allow stop magnet 541 to act very quickly when the proper terminal set is found. When the proper terlnlnal is found, stop magnet 541 is energized due to the completion of a circuit for magnet 541 in parallel with that just traced for the left-hand winding of relay 543. Magnet 541'l is now fully energized and Arelay 543 is sufficiently energized to attract its armature, thus breaking the driving circuit,

of power magnet 540 and causing relay 543 to include both its right and left-hand windings in a holding circuit.

Referring now to Fig. 3, it will be observed that as soon as relay 543 becomes energized a circuit is completed from grounded battery, power magnet of sequence switch 200, lower left-hand contact of sequence switch spring 219, lett-hand armafture and back contact of relay 223, conductor 227, outer lett-hand armature and front contact of relay 543 to ground for moving this sequence switch out of position 3 and into a position determined by the setting of the translator switch. The sequence switch 200 is the sequence switch which determines the class and routing of the call and in accordance with its setting will be determined the number and kind of impulses to be sent, Vthat is, whether otiice impulses will be sent, whether relay call indicator impulses will be sent, whether the call will be directed to a special operator, or any of fthe various combinations essential in a large installation.

The extentlof motion of sequence switch 200 will be determined by the point in its operation at which relay 223 is energized. Relay 223 has its circuit successively extended to conductors 228. 229, 230, 231, 232, 233, 234, 235 and 236 as the sequence switch moves through its various positions. These conductors extend to various terminals in the contact banks of the translator. To avoid complexity of the circuits, these leads have. not been carried down tothe translator bank terminals, a single conductor 553 being utilized to indicate the manner in which these contacts will be connected to the arc of contacts which controls the positioning of the. class register.

Since it has been assumed that 'the call is to be an interoiiice, full mechanical call, the class register, that is the sequence switch 200, will be brought to rest in position 7.'

Toy accomplish this, lead 229 would have rto be wiredto the No. 12 terminal in the class are of the contact bank served by the T? brush set of the translator. If we assume this to be the case, fthen when sequence switch 200 reaches position 6%, a circuit is completed from grounded battery, winding of relay 223, upper left-hand and lower right-hand contacts of sequence switch spring 237, conductor 229, brush 554, conductor 555, inner left-hand armature and front contact of relay 543 to ground. Relay 223 is energized in this circuit and' locks up through its inner-right-hand armature and front contact and the,lower contact ot sequence switch spring 238 to ground. The

energization of relay 223 opens the driving circuit of sequence switch 200 and brings this switch to ,rest in position 7.

The energization of relay 223 also completes a circuit from grounded` battery,`

powe-r magnet of sequence switch 300, Fig. 6, the upper right-hand contact of sequence switch spring 313, conductors 314 and 315,-

armature and front contact of relay 543 to?y ground, for moving this sequence switch out of position 1 and into position 2.

As soon as sequence switch 300 reaches position 2 a circuit is completed from grounded battery, left-hand winding of relay 107, lower left-hand and upper righthand contacts of spring 112, inner righthand armature and front contact of relay 121, sender selector brush 132 and its associated contact, conductor 133, outer righthand armature and back contact of relay 239, upper right-hand contact of sequence switch spring 240, conductors 241 and 316, inner right-hand armature and back constact of relay 317, lower right-hand contact of sequence switch spring 318, winding of stepping relay 320, armature and back con-l tact of relay 321, which is connected in parallel with the 0 counting relay, inner left-hand armatura and back contact of relay 306, resistance 322, upper left-hand contact yof sequence switch spring 312, to ground. Relays 107 and 320 are energized in this circuit.

The energization of relay 107 completes a circuit from grounded battery, power magnet of sequence switch 100, lower righthand contact of sequence switch spring 116, inner righthand armature and front contact of relay 107, lower contact of sequence switch spring 117, to ground, for moving sequence switch 100 out of position 3 and into position 4. Relay 107 remains energized in position 4 of sequence switch 100, due to the closure of a locking circuit extending from grounded battery, left-hand winding of relay 107, left-hand armature f and front contact of relay 107, conductors 110 and 111. upper left-hand contact of sequence switch spring 112, to ground over fthe path described.

In position 4 of the sequence switch a circuit is completed for 11p-drive magnet 134. This circuit extends from grounded battery, winding of magnet 134, upper right-hand contact of sequence switch spring 1,20, inner yright-hand armature and front contact ot relay 107, lower contact of sequence switch spring 117 to ground. The energization of magnet 134 causes the district selector to advance its brush shaft in a brush selecting movement.

Referring now to Fig. 6, it will he ob.

n quence switch spring 309, outer left-hand armature and back contact of relay 308, outer left-hand armature and back contact of relay 307, inner right-hand armature and back contact of relay 306, conductor 305, lower right-hand contact of sequence switch spring 304, upper left-hand contactof sequence switch spring 323, lower right-hand contact of sequence switch spring 409 (which it will be remembered, is'controlle'. by the class register switch shown in Fig. 3, and is therefore closed in position 7), conductor 410, translator brush 556, which is in engagement with the twelfth terminal of the T2 contact bank, and thence through the winding of one of the counting relays to grounded battery. .1

In order to simplify the disclosure, the wiring of the counting relays to the various Contact sets in the translator bank has not been shown. It will be assumed, however,

that with the translator set with'one of its brush sets in engagement with the twelfth thereby will be selected at the district.

switch. It will further be assumed that with the same setting the second brush set and the. third group served thereby will be selected by the office selector switch.

Under the assumption made, contact No. 12 in the are served'by brush 556 will he connected to the N o. 2 counting relay; contact No. 12 served by brush 557 will be connected to the No. 3 counting relay; contact No. 12 served by brush 558 will be connected to the No. 1 counting relay and contact No. 12 in the arc served by brush 559 will be connected to the No. 2 counting relay.

Bearing these assumptions in mind, the circuit which is completed upon the energization of stepping relay 320 will then extend from brush 556 to the winding of the No. 2 counting relay, Fig. 6, to grounded battery. The No. 2 counting relay is energized in this circuit and prepares, in the well-known manner, a circuit for the No.

l'2 counting relay by way of conductor 324,

lower right-hand contait of sequence switch spring 325, conductors- 326 and 327` to ground, at sequence switch spring 312. The winding of the No. 2 counting relay is, however, shunted by the ground controlled at the armature and front contact of relay 320 and does not energize at this time.

llos

' As soon as the district brush has advanced av suilicient distance to allow the commutator brush to engage the first conducting segment of commutator 136, stepping relay 320 is shunted down, since the locking circuit of relay 107 now extends from grounded battery, left-handwinding of relay 107, left-hand armature and front -contact of relay 107, conductors 110 and 

